Problem: $-\dfrac{3}{6} - \dfrac{5}{10} = {?}$
Explanation: $ = - {\dfrac{3 \times 5}{6 \times 5}} - {\dfrac{5 \times 3}{10 \times 3}} $ $ = - {\dfrac{15}{30}} - {\dfrac{15}{30}} $ $ = - \dfrac{{15} - {15}}{30} $ $ = -\dfrac{30}{30}$